The present invention relates to a height adjustment arrangement for seats, particularly motor vehicle seats.
Height adjustment arrangements of the above mentioned general type are known in the art. In a known height adjustment arrangement, a seat part is raisable and lowerable with the aid of pivotable supports arranged in the region of each seat corner. The pivotable supports are moved by a slide device including a thread spindle and an axially immovable nut engaged with the latter, and have one end arranged at a fixed height and another end hingedly connectable with the seat part. Such a height adjustment arrangement is disclosed, for example, in the German Offenlegungsschrift No. 2,846,632 and has adjusting drives surrounding the pivotable supports at four corners of the seat portion and formed as structural units. The adjustment drives are components of a frame which is arranged on a frame of the vehicle floor or on the guiding elements arranged on the vehicle floor. The pivotable supports are mounted rotatably in the housing of the adjustment drive at their one ends and pivotably connected with their free ends on a frame supported on the seat portion. The adjustment drives are assembled in pairs in the region of the seat front side and the back part of the seat and selectively driven by a motor separately from one another. The above described height adjustment arrangement has a complex construction which is relatively expensive both in the sense of the material consumption and the manufacturing and mounting of the same. Moreover, it is necessary to provide for such a height adjustment arrangement a lower frame mounted on a vehicle bottom or on a guiding elements and connected via the pivotable support with an upper frame mounted on the seat portion.
Such a frame construction is also utilized in the German Offenlegungsschrift No. 2,717,416. In this adjustment arrangement a lower structure forming a lower frame is mounted on a vehicle floor or guiding element and is connected via the pivotable supports with supporting arms forming an upper frame. The pivotable supports are height adjustable by an adjustment drive containing a braking spring coupling with a braking drum mounted on the upper frame. A helical rotary spring abutting against the braking drum provides for fixation of an adjustment shaft which supports a toothed wheel engaging with a toothed segment of a pivotable support, wherein the adjustment shaft can be actuated by a lever for releasing purposes. This height adjustment arrangement also includes a lower frame mountable on the vehicle floor or vehicle guides, and an upper frame connectable with the seat portion, wherein the upper frame and the lower frame are connected with one another by the pivotable supports. Thus, this height adjustment arrangement also has an expensive frame structure which forms a separate structural group between the vehicle floor and the seat portion.